2. THE CONTINUUM

The continuum emission is one of the primary channels by which AGN
release energy. The physical understanding of the various mechanisms
which give rise to the continuum is still rather rudimentary, and at
least some of the proposed (textbook) explanations may lack relevance
altogether. One significant step forward could be the growing number
of multiwavelength, coordinated observational campaigns from
observatories both on Earth and in space. In spite of this, the
spectral coverage is at present far from complete, leaving the
bolometric luminosity undetermined in many sources. The unobserved
extreme UV (EUV) region is one particular example.

Non-blazar continuum spectra are often assumed to contain an
underlying power law

(5)

with a spectral index ~ 1,
extending over a range of 104 in
frequency (from IR to X-rays), on top of which various bumps are
superposed. A generic AGN spectrum is given in Fig. 2.